The bio-diversity of the particular place when comes under threat it is called Hot spot or sensitive spot. Indian subcontinent has unique geographical positions, distinct physiographic, edaphic and climate zones and gradients. This subcontinent abodes a very rich and diverse flora and fauna with high percentage of endemism.
It is placed 10th among the plant rich nations of the world and 4th among the Asian countries. Out of 25 most important global Hot spots of biodiversity two are present in India i.e., Eastern Himalayas and Western Ghats. Based on the uniqueness of the phytogeographical zones and pattern of endemism 25 micro hot spots also have been identified in India.
Hot spots cover less than two per cent of the planet’s land surface but contain more than 50 per cent of its terrestrial biological diversity. In these Hot spots the ecosystems are at greatest risk.
Less than 10 per cent of other original natural habitat is remaining. In the Mediterranean Basin, only two per cent is present. One aspect of the hot spots is that almost 40 per cent of all terrestrial plants and at least 25 per cent of vertebrate species are endemic to these areas.
Hot spots include Mediterranean basin, tropical Andes in South America, Madagascar and Indian Ocean islands, South Africa’s cape floristic province, South west Australia, large areas around Indonesia, Malaysia and the Philippines and Eastern Himalaya.
There are no designated Hot spots in the area of the former Soviet Union. Though large extent of forest is found but in terms of Bio-diversity priority it is much lower than the tropical rain forests.
Areas with high levels of species richness, threat and endemism are known as Hot spots. Myers 1988 for the first time identified 10 tropical forest hot spots with high level of plant endemism and a serious level of habitat loss. Myers (1960) added 8 more hot spots including 4 Mediterranean-type ecosystems.
Again in 2000 Myers identified more hot spots and identified 25 biodiversity hot spots. These 25 hot spots contain 44% of the world’s plants as endemics and 35% of the terrestrial land vertebrates in an area of 1.4% of earth’s land surface. Recently 34 Bio diversity hot spots have been identified.
For being a Hot spot a region must contain at least 1500 species of Vascular plants i.e., 70.5% of the world’s total flora as endemics and it has to have lost at least 70% of its original habitat.
The 34 Hot spots distributed in various regions of the world are listed below:
A. North and Central America:
(1) California Floristic Province,
(2) Caribbean Islands,
(3) Madrean Pine-Oak Woodlands, and
(4) Mesoamerica.
B. South America:
(5) Atlantic forest,
(6) Corrado,
(7) Chilean Winter Rainfall-Valdivian forest,
(8) Tumbes-Choco-Magdalena, and
(9) Tropica Andes.
C. Europe and Central Asia:
(10) Caucasus,
(11) Irano-Anatolian,
(12) Mediterranean Basin, and
(13) Mountains of Central Asia.
D. Africa:
(14) Cape floristic region,
(15) Coastal forest of eastern Africa,
(16) Eastern Afromontane,
(17) Guinean forests of West Africa,
(18) Horn of Africa,
(19) Madagascar and Indian Ocean islands,
(20) Map utaland-Pondoland-Albany, and
(21) Succulent Kareo.
E. Asia Pacific:
(22) East Malasian Islands,
(23) The Himalaya,
(24) Indo-Burma,
(25) Japan,
(26) Mountains of South West China,
(27) New Caledonia,
(28) New Zealand,
(29) Philippines,
(30) Polynesia-Micronesia,
(31) South West Australia,
(32) Sundarland,
(33) Wallacea, and
(34) Western Ghats and Sri Lanka.
Global warming and extinction of endemic species from Bio-diversity hot spots was studied in detail and published in Conservation Biology. The potential impact of climate change and global warming on 23 of the world’s tropical hot spots of biodiversity places are identified. It includes Southwest Australia, Caribbean, New Zealand, Madagascar, Tropical Andes and Mountains of China.
In India Prof. Madhav Gadgil worked at the centre for Ecological Sciences, Indian Institute of Science and Biodiversity Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore on the ecology of Western Ghats, (a mountain range in South India) which is a biodiversity hot spot.
Western Ghats and Sri Lanka:
The Western ghats of South West India arid the highlands of South Western Sri Lanka, are separated by 400 Kilometres. They are strikingly similar in their geology, climate and evolutionary history.
Western Ghat’s commonly known as Sahyadri hills and formed by Malabar plains and the chain of mountains running parallel to India’s West Coast, about 30-50 Km island. Western ghats run all along the Arabian Sea from Tapti in Gujarat to Mahendra Gir in Tamil Nadu. It covers and area of about 160,000 km2 and stretch for 1,600 km from the country’s southern tip to Gujarat in the north. It is interrupted only by the 30 Km Palghat Gap.
Western Ghats mediate the rainfall of peninsular India by intercepting the south western monsoon winds. Western slopes of the mountains experience heavy annual rainfall, while the eastern slopes are drier, rainfall also decreases from south to north.
Many rivers originate from these mountains which are source of drinking water, irrigation, and power. Wide variation of rainfall pattern and complex geography results in great variety of vegetation types in Western Ghats. Scrub forests in low lying rain-shadow areas and the plains, deciduous and tropical rain forests are the major areas. Rolling grasslands are also present.
Sri Lanka is a continental island separated from southern India by the 20 meter-deep Palk Strait. The island is 67,654 km2 in size, repeatedly connected with monsoon winds, resulting in much of the island experiencing relatively low rainfall, except for the south-western “West Zone” quarter, where precipitation ranges up to 5000 nm per year.
Dry every-green forests occupy the dry zone. Dipterocarpus dominated rainforests dominate the low lands of the wet zone. 220 km2 of tropical montane cloud forest is present in the central hills rising upto 2,524 meter altitude.
Coral reefs support the livelihood of millions of people by supplying sea food, building material, medicinal products and attract tourism revenue also. Reefs protect Shoreline and communities from storms erosions. The coral reefs are deeply threatened by human activities and global climate change.
There are about 11 coral reef Hot spots. They are as follows:
1. Philippines:
It is ecologically unique island that is highly diverse. Destructive fishing methods using explosives and poison, excessive fishing, pollution etc., are threatening the species. This is one of the most threatened hotspots due to its population density.
2. Sundaland:
It covers western half of the Indonesian Archipelago i.e., Bali, Java, Sumatra, Borneo etc., Malaysia and a part of Thailand. It is a part of Coral Triangle which is most diverse coastal area on the planet; rich in marine species and a large occurrence of endemism.
3. Wallacea:
This hot spot covers Nusa Tenggara, the molluscas and sulawesi. It is divided from Sundaland by the Wallacea line. Major threats are pollution from land-based sources, Live reef fish trade, destruction of fishes, sediment pollution etc.
4. Gulf of Guinea:
It consists of four islands of the Gulf of Guinea, off the west African coast. The water is not salty due to the presence of river.
5. Eastern South Africa:
It is present adjacent to Cape floristic. The major threats are land-based sources of pollution, fishing etc.
6. North Indian Ocean:
It covers Maldives, Chagos islands and much of the Lakshadweep and Lakkadives archipelagoes, as well as Sri Lanka. Global warming in 1998 increased the sea surface temperature destroying the corals.
7. Southern Mascarene Islands:
It surrounds the islands of Mauritius, La Reunion and Rodriguez in the Southern Indian Ocean. Rapidly growing human population, pollution etc. are the threats to it.
8. Cape Verde Islands:
It is present in the mid-Atlantic off the west African coast Major threats are coastal development, pollution from land clearing and agriculture.
9. Southern Japan, Taiwan and Southern China:
It extends from Kyushu in Japan, through Taiwan to the coast of southern China. Shoreline development and conversion for aquaculture and agriculture etc. are the major threats.
10. Western Caribbean:
Hotspot covers the Caribbean islands and coastal reef from the Mexican Yucatan Peninsula to Colombia. Major threats are epidemic diseases and coral bleaching due to global warming.
11. The Red Sea and Gulf of Aden:
This hotspot extends for 2500 Km from north to south including the Gulfs of Aquaba and Suez. Major threats are coastal and industrial development, oil from tankers.
Hottest Hot spots of India:
1. Andaman and Nicobar Islands,
2. Arvalli Hills (Rajasthan),
3. Bharatput Lake and Wetland (Rajasthan),
4. Chilka Lake (Orissa),
5. Dal Lake (Jammu and Kashmir),
6. Doon Valley (Uttaranchal),
7. Gir Forest (Gujrat),
8. Himalayas (India/Nepal),
9. Kodai Lake (Tamilnadu),
10. Little Rann of Kutch (Gujrat),
11. Loktal Lake (Manipur),
12. Manas (Assam),
13. Nilgiri Hills (Tamil Nadu),
14. North-eastern Himalaya (India),
15. Narayan Sarover (Gujrat),
16. Ooty Lake (Tamil Nadu),
17. Pooyam Kutty Valley (Kerala),
18. Palni Hills (Tamil Nadu),
19. Pulikat Salt Water Lake (Tamil Nadu),
20. Renuka Lake and West land (Jaryana),
21. Silent Valley (Kerala),
22. Sariska (Rajasthan),
23. Sunderbans (West Bengal),
24. Shivalik Hills (Himachal Pradesh),
25. Thar desert (Rajasthan), and
26. Western Ghats (India).